Grout Calculator: Cubic Inches, Cubic Feet, Gallons

The volume of grout needed to fill the space between tiles depends on the total size of the tiled area, tile size, space between the tiles, and depth of the grout. If you know the values of these project parameters, you can accurately estimate the cubic inches, cubic feet, or gallons of grout needed. You can apply the formula below using pen and paper, or use the convenient calculator on the left.

First, compute the proportion of the space that is covered with tile but not grout. If each tile has a width of X inches, a width of Y inches, and grout spacing of s inches, then the proportion is

XY/[(X+s)(Y+s)].

Next, compute the proportion of space that is covered with grout using the equation

1 - XY/[(X+s)(Y+s)].

Multiply this number by the depth of grout in inches, d. And finally, multiply by the total area of the space in square inches, A. If you know the area in square feet, multiply by 144 to convert to square inches. (If using the calculator, you do not have to make this conversion, the calculator does it for you.) The final expression for the cubic inches of grout is

Ad(1 - XY/[(X+s)(Y+s)]).

To convert this to cubic feet, divide by 1728. To convert cubic inches to gallons, divide by 231.

Example: Hank is tiling 150 square feet of floor space with tiles that are 4 inches by 4 inches. The space between the tiles is 0.25 inches and the grout is filled to a depth of 0.25 inches.

The values we have are

A = 150(144) = 21600 square inches
X = 4 inches
Y = 4 inches
s = 0.25 inches
d = 0.25 inches

Plugging these values into the formula gives

(21600)(0.25)(1 - (4)(4)/[(4.25)(4.25)])
= (5400)(1 - 16/18.0625)
= (5400)(0.114187)
= 616.61 cubic inches
= 0.3568 cubic feet
= 2.667 gallons

You should buy more than this amount so that you have enough grout to finish your project.

© Had2Know 2010